Resonance shield for high pressure short-arc lamps



United States Patent Inventors Teddy J. Peacher;

Dorwin L. Kilbourn, Huntsville, Ala. 789,529

Jan. 7, 1969 Dec. 22, 1970 The United States of America as represented by the Secretary of the Army Appl. No. Filed Patented Assignee RESONANCE SHIELD FOR HIGH PRESSURE SHORT-ARC LAMPS 3 Claims, 2 Drawing Figs.

U.S. Cl 313/113, 313/184, 313/205,313/2l4, 313/220 Int. Cl H01j 5/16 Field ofSearch 313/1 13, 184,214, 220, 205

[56] References Cited UNITED STATES PATENTS 3,054,921 9/1962 L 313/220X 3,280,360 10/1966 Frost et a1 313/113X FOREIGN PATENTS 462,858 3/1937 Great Britain 313/184 Primary Examiner-Raymond F. Hossfeld Attorneys-Harry M. saragovitzt Edward .1. Kelly. Herbert Berl and Harold W. Hilton ABSTRACT: A short-arc lamp having means for limiting resonances occurring therein. The lamp includes an envelope enclosing a cathode and an anode in a large cavity. A tubular shield member carried in the cavity encloses the anode and cathode, whereby the effective size and shape of the cavity is reduced and the resonances occurring in the modulated plasma is restricted by the dimensions of the tubes inner surface and plasma density.

RESONANCE SHIELD FOR HIGH PRESSURE SHORT- ARC LAMPS BACKGROUND OF THE INVENTION Conventional high-pressure short are gas lamps exhibit acoustical resonance modes when electrically modulated. The resonance frequencies are dependent upon the size and shape of the arc cavity. Attempts to electrically modulate a lamp near one of the resonance frequencies can result in arc extinction.

SUMMARY OF THE INVENTION The present invention relates to an arc lamp having means for limiting resonances set up responsive to modulations in the enclosed gas. The lamp includes an envelope enclosing an anode and cathode in a gas filled cavity. A housing of quartz or ceramic encloses the anode and cathode to effectively reduce the size of the cavity and restrict the lowest frequency at which resonance can occur to the inner diameter and gas density.

It is, therefore, an object of the present invention to provide an arc lamp withresonance shield means to limit resonance in the lamp resulting from modulation of energized gases in the lamp.

These and other objects and advantages of the invention will be more readily apparent from the following detailed description and drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an elevational sectional view of the arc lamp of the present invention.

FIG. 2 is a sectional view along 2-2 on reduced scale.

DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in FIGS. 1 and 2 an arc lamp is shown to include an envelope 12 having an internal surface 14 disposed to serve as a beam forming reflector. A ceramic insulating ring 16 is secured to a flanged portion 17 of envelope 12. A ring like spider support member 18 is-secured to the other side of ring 16 and is provided with a plurality of inwardly extending legs 19 for support of a cathode 20 therein. Legs 19 are secured to an inner surface 23 of member 18 and extend inwardly for secured relation with cathode 20. Legs 19 are secured to member 18 and cathode 20 in conventional manner, such as by welding, brazing, etc. A retaining ring 21 serves to hold a sapphire window 22 adjacent a cathode 20. Ring 21 also serves as a conductor for cathode 20. A base member 24 is secured to envelope 12 and serves as a support for the anode 26 which extends from the base portion into a gas filled cavity 28 formed by the envelope. A support member 34 is carried in housing 30 for support of the anode thereon.

To restrict resonances occurring in the modulated gas, a housing 30 of quartz or ceramic material is secured around the anode and cathode. The housing is a cylindrical collar extending out of the base 24 and into the envelope in enclosing relation with the anode and cathode. A fill tube 32 communicates into the interior of the envelope for directing gas therein. A wire wrap or spring 33 is disposed around the cathode adjacent the end of housing 30 to prevent the tube from moving, since the tube is only loosely mounted about the electrodes and is not vacuum sealed thereto.

Because of the large cavity size, the somewhat hemispheri cal shape of the cavity and density of the gas, standing waves whose frequencies fall in the audio range can occur. However, the tubular housing 30, which is mounted in the lamp with a loose fit, effectively reduces the size and shape of the cavity. The modulations of the plasma are, therefore, limited to the inside dimensions of the tube with some damped oscillations escaping around the ends of the tube 30; The lowest frequency at which resonance can now occur will be restricted by the dimension of the tube s inner diameter and the gas density.

to be understood that various modifications may be It rs resorted to by one skilled in the art, however, such modifications are within the spirit and scope of the appended claims.

We claim:

1. A high-pressure gas are lamp structure comprising:

a. a gas filled envelope having a mirrored internal reflecting surface; an anode and cathode mounted in said envelope in axial alignment;

c. means for support of said anode and cathode in said envelope, said cathode support means including an annular member secured to said envelope and provided with a plurality of legs inwardly extending into the interior of said envelope, said legs disposed in secured relation with said cathode;

d. shield means comprising a tubular member loosely secured about said anode and cathode for limiting resonant frequencies occurring in said envelope responsive to energization and modulation of said gas;

e. means disposed between said shield means and said plurality of legs to retain said shield! means in the loosely secured relation while preventing displacement thereof.

2. The device as set forth in claim 1 including a base member secured to said envelope and having said anode mounted therein, said base member provided with an opening in communication into the interior of said envelope.

3. The device as set forth in claim'2 wherein said shield means is quartz. 

